Early in his presidency, Lyndon Johnson inspired enormous hope. But the promise for a Great Society imploded — and disappointment jolted many former supporters, with trust and optimism turning into alienation and bitterness. The negative ripple effects lasted for decades.

Fifty years after Johnson entered the White House, the corrosive aspects of his legacy are easy to discern. A political base for progressive social change eroded as he escalated the Vietnam War and bought time with shameless deceit. For many people, distrust of leaders became the essence of realism.

Initiating a disastrous mix of rhetoric and carnage, Johnson told the nation on Aug. 4, 1964, “We still seek no wider war.” On the same day, he ordered bombing of North Vietnam in tandem with bogus claims that its navy had attacked U.S. ships in the Tonkin Gulf.

Throughout his full term after a landslide victory in the November 1964 election, LBJ continued to claim benign intent in Vietnam. “I do not genuinely believe that there’s any single person anywhere in the world that wants peace as much as I want it,” Johnson said on May 17, 1966. In mid-January 1968, he insisted that “our goal is peace — and peace at the earliest possible moment.”

For many citizens, the president’s willingness to lie while pursuing indefensible policies caused massive — and perhaps irreversible — distrust and even enmity toward the U.S. government. As a consequence, millions came to see history and current events in a starkly clearer light. By the time Jimi Hendrix performed the national anthem at Woodstock five years after Johnson’s Gulf of Tonkin speech, an unprecedented number of Americans heard the musical bombs bursting in air as horrific instead of noble.

Forty years later, the new presidency of Barack Obama was awash in a strong tide of good will, comparable, in its own way, to the wave of public sentiment that lifted Johnson as the new president after the Nov. 22, 1963, assassination of John F. Kennedy. Obama had run and won on hope, and his victory — while not of Johnson’s landslide proportions — provided major momentum.

Obama pursued policies that largely undercut his lofty oratorical appeals to his base. Deference to corporate power, the military-industrial complex and the national-security surveillance state — coupled with scant action on the vastly important matter of climate change — turned him into another president eager to cater to the intersection of Wall Street and Pennsylvania Avenue.

Like Bill Clinton before him, Obama took care of himself and let others shoulder the political consequences. After Clinton and Obama stocked their administrations with corporate heavyweights, their rebuffs to progressive populism went over big with corporate media outlets. But the policy choices dispirited and demobilized the Democratic base, ushering in GOP takeovers of the House in 1994 and 2010.

Taking care of No. 1, Clinton and Obama won second terms, but on paths strewn with wreckage.

Such betrayals have grim effects. The damage to the body politic is akin to the results of backroom rubber hoses, inflicting internal injuries without leaving visible marks.

The best way to not become disillusioned is to not have illusions in the first place, but such axioms may seem like facile hindsight. Rather than turn cynical and fatalistic, prior supporters should quickly and directly challenge leaders who have disappointed them. Such challenges were sparse during the first years of the Obama administration, and they are still inadequate.

Living in a mass culture that encourages political passivity, all too many of Obama’s ex-enthusiasts have drifted into quiet disengagement instead of creative enragement. While recent years have seen an upsurge of activism on issues that range from climate change and economic justice to civil liberties and war, the magnitude and intensity of such efforts must increase.

On civil liberties, for example, the American Civil Liberties Union and other advocates have condemned the Obama administration as the worst in memory. But Obama remains obstinate. In response to chilling revelations by National Security Agency whistle-blower Edward Snowden, the president has circled the surveillance wagons. He insists on repeating falsehoods along the lines of his claims on national television last August that “we don’t have a domestic spying program” and “there is no spying on Americans.”

No more credible than Johnson’s claims of peaceful intent, such assertions from Obama have accelerated the estrangement among many of his most fervent past supporters — particularly young adults whose active enthusiasm and votes carried him into the White House. When I attended the Stop Watching Us rally near the Capitol in Washington in October, the crowd was younger than I had seen at any other demonstration in recent years.

In many ways, of course, the political milieu of five decades ago is a far cry from today. But the fundamental betrayal of popular optimism by the president is eerily similar, as may be its consequences. Smoldering anger and festering disaffection may be hard to gauge, but the resulting corrosion has cumulative effects. Dreams make history; so do disappointment and despair. The poison of a leader’s betrayal can course deep. The antidotes must include idealism and determination.

Norman Solomon is co-founder of RootsAction.org and founding director of the Institute for Public Accuracy. His books include “War Made Easy: How Presidents and Pundits Keep Spinning Us to Death.”

Norman Solomon is executive director of the Institute for Public Accuracy, where he coordinates ExposeFacts. Solomon is a co-founder of RootsAction.org, which has encouraged donations to the Sterling Family Fund. Disclosure: After the guilty verdict five months ago, Solomon used his frequent-flyer miles to get plane tickets for Holly and Jeffrey Sterling so they would be able to go home to St. Louis.